The reproductive epidemiology project emphasizes the development and application of methods for measuring human reproductive damage. Reproductive damage can include infertility, sub-clinical early fetal loss, spontaneous abortion, impaired fetal growth, and low birthweight. Each of these outcomes can be produced by environmental factors, and each represents a possible endpoint for detecting the effects of toxins on human reproduction. One major component of this project is the study of fertility. Time-to-pregnancy (that is, the number of cycles a couple takes to conceive) is being developed as a potentially sensitive measure of fertility. This approach will be used in a study of reproductive outcomes among dental technicians exposed to mercury. A secon component of this project is the study of very early pregnancy loss. In a prospective study of 230 women who have stopped using birth control in order to become pregnant, daily urine specimens have collected in order to test for evidence of pregnancy. This will provide an estimate of the extent of early pregnancy loss in humans. The risk of early loss will be studied in relation to common exposures in this populaton, such a use of alcohol, tobacco, caffeine beverages and medications. Work continues on the development of a method for the analysis of birthweight and perinatal mortality.